The invention relates to a working procedure for an internal combustion engine and in particular this invention relates to an internal combustion engine incorporating a first cylinder having a displaceable first piston therein which is connected to a crank shaft, and a first cylinder volume which is formed between the first piston and the first cylinder and which is adapted to be filled via a fresh gas inlet with fresh gas during the expansion thereof in the course of a suction stroke, whereby the fresh gas is adapted to be compressed during a subsequent compression stroke where the first cylinder volume is reduced in size.
In the case of known combustion engines using internal combustion, the combustion chambers relating to a respective cylinder (e.g., amongst others, engines of the Ricardo, Perkins, Hercules, Deutz, ACO type) are arranged statically in the cylinder head, the engine block and/or in the engine pistons. A proposal, which remains theoretical but which envisaged, includes a rotating combustion chamber in which a partial quantity of a fatty mixture was to be burnt, was disclosed in European Patent Application No. EP-A-0 074 174, it being intended that this mixture should then be used as an igniter for a weaker mixture contained in the conventional combustion chamber.
A feature common to all the embodiments was the short time period that was available for the evaporation of the fuel and the burning thereof, which was necessitated by the construction and the procedures adopted. A further disadvantage was that the combustion process took place in a variable volume and that it had to occur at approximately xe2x88x9215xc2x0 before and up to +35xc2x0 after the top dead center position. As a consequence thereof, there was incomplete combustion of the fuel, which results in the production of harmful exhaust gases. In the case of fuels which require more time for the preparation of the mixture (diesel) or for the combustion thereof (alcohol), there is an additional limitation with regard to the maximum possible rotational speed. The available combustion period is in the general order of magnitude of approximately 0.001 seconds. The compromises created include as illustrative examples: increasing the excess quantity of air or accepting an incomplete combustion process lead to a lowering of efficiency as well as an increase in the emission of harmful materials. In the case of the known working procedures, a reduction in the quantity of excess air would lead to incomplete combustion, to further energy losses and also to an increase in the emission of harmful substances. An increase in the theoretical efficiency by reducing the temperature of the exhaust gas is only made possible through increased expenditure for the apparatus.
In order to prolong the time required for preparing the mixture and for prolonging the combustion period, the fuel may be premixed with air in a carburetor, or, in the case of indirect fuel injection, in the suction channel intake, although the problems can only be reduced to a limited extent thereby.
An aspect of the present invention is to achieve improvements and especially higher performances, a higher level of efficiency and preferably good exhaust gas values in comparison with the conventional working procedures and internal combustion engines.
In accordance with the present invention, this aspect is achieved in the case of the working process or procedure mentioned hereinabove in that a fresh gas is compressed in a first cylinder volume incorporating a first piston during successive compression strokes and the compressed gas is then forced into one of at least two combustion chambers in which combustion of a mixture consisting of the compressed fresh gas and at least partially evaporated fuel is initiated after the combustion chamber has been closed relative to the first cylinder volume, whereafter the combustion chamber is opened relative to a second cylinder volume and the expanding combustion gases from the combustion chamber are applied to a second piston in the second cylinder volume for performing a working stroke and following the completion of the working stroke, exhaust gases are expelled from the second cylinder volume.
In the case of the internal combustion engine mentioned hereinabove, this aspect is achieved in that, outside the first cylinder volume, there are provided at least two mutually separated combustion chambers into which a compressed fresh gas, which is chargeable with fuel and is ignitable therein, is adapted to be alternately fed from the first cylinder volume during successive compression strokes, and, following the ending of a respective compression stroke, each of the combustion chambers is connectable during a working stroke to a second cylinder volume which is formed between a second cylinder and a second piston that is connected to the crank shaft, whereby the second piston is displaceable by the ignition of the compressed fresh gas that is charged with fuel in such a manner that the second cylinder volume will be expandable, and exhaust gas will be expellable by the second piston from the second cylinder volume during an exhaust stroke occurring subsequent to the working stroke.
Thus, in accordance with another aspect of the present invention, it is envisaged that the suction intake port and compression strokes should be spatially separated from the working and the exhaust strokes and that they should be carried out in two different cylinders. Between these two cylinders, there are disposed at least two combustion chambers into which the fresh gas that was compressed by the first cylinder is successively, i.e., in a cyclical sequence, fed during the compression stroke or towards the end of the compression stroke.
Advantageously, the combustion chambers are closed relative to the first cylinder volume towards the end of the compression stroke, for example, at the top dead center position of the first piston following the compression stroke. Since the combustion process is not initiated in the first cylinder volume used for compression purposes, the engine is not inclined to ignite the compressed fresh gas mixture prior to the top dead center position of the first piston and thus to premature formation of a high pressure.
Thereafter, fuel can be supplied, by means of an injection nozzle for example, into the combustion chambers, which are separated from the two cylinder volumes, at a selected time point in dependence on the desired evaporation period and ignition period and following the desired evaporation period, the ignition process can be initiated by means of a spark plug. Due to the fact that the fuel is injected into the previously emptied hot combustion chamber, the process of evaporation or mixture-preparation and distribution of the fuel in the fresh gas is extremely efficient, such efficiency not generally being attainable, for example, in the case of a conventional internal combustion engine using an injection process prior to the top dead center position. The ignition process, which is effected by means of a spark plug, can take place at a desirable time point prior to the opening of the combustion chamber relative to the second cylinder volume which is then at the start of the working stroke, whence the combustion process will have been completed or finished to a sufficient extent before the gas reaches the second cylinder volume. Hereby, the ignition process can be initiated at a suitable position within the combustion chamber so that the combustion gases will expand in an appropriate manner into the second cylinder volume. Advantageously, the flame front will expand in a direction opposite to this expansion of the combustion gases flowing into the second cylinder volume.
It is also possible for the ignition process to take place at a time point at which the combustion volume is already open relative to the second cylinder volume.
Basically, it is possible for the first cylinder and the second cylinder to have different capacities so that one can then optimize the compression and the working strokes. However, it is also possible to use a construction involving equal cubic capacities. It is advantageous if the cylinder volumes correspond to the swept volumes so that the first cylinder will have a practically negligible compression space and the compressed gas will be transferred in its entirety into the combustion chamber. Since the first cylinder volume, i.e., compression volume is subsequently refilled with fresh gas or air; the residual amounts of air will not cause interference. The compressive power stored in the residual air can be ritualized during the suction stroke. Due to the fact that the capacity of the second cylinder volume, advantageously, substantially corresponds thereto and that a negligible compression space remains in the second cylinder volume at the top dead center position of the second piston, the exhaust gases can be transferred to an exhaust channel port virtually in their entirety at the upper dead center position of the second piston. The residual exhaust gases do not lead to power losses since the power stored therein is ritualized during the following working stroke.
The combustion chambers can be arranged, advantageously, in a rotatably mounted body which is driven in synchronism with the crank shaft and thus in synchronism with the first cylinder and the second cylinder. Consequently, a good match between the stroke cycles of the cylinders and the combustion volume can be obtained. In the case of an Otto engine it is advantageous to have exactly two combustion chambers and to have four combustion chambers in the case of a diesel engine, these chambers being filled alternately with equal amounts of fresh gas and initiating the combustion process. In particular, the rotatably mounted body may be a combustion shaft that, for example, has a circular cross-section and is advantageously mounted in parallel with the crank shaft. Consequently, it can be filled in the radial direction thereof with fresh gas from the first cylinder through its upper outlet and it can transfer the ignited fresh gas in the radial direction thereof into the second cylinder volume. To this end, a respective portion of the circular cross-section combustion shaft projects by an appropriate amount into the cylinders, for example, a 90xc2x0 segment of the circular cross-section of the combustion shaft, so that it can receive or expel gases over a large boundary surface area when a combustion chamber is opened. It is advantageous if the piston is adapted to this shape of the portion of the combustion shaft projecting into the cylinders so as to at least generally close the cylinder volumes at the top dead center position.
The two cylinders may be mutually separated in the axial direction of the combustion shaft so that it will be possible to transport the fresh gas more easily from the first cylinder volume to the second cylinder volume via the combustion shaft. The combustion shaft may, for example, comprise two combustion chambers and be rotated utilizing a step-down ratio of 2:1 relative to the crank shaft, preferably, being directly driven thereby. Consequently, the two combustion chambers can be alternately filled with compressed fresh gas, receive the fuel and expel substances into the second cylinder volume after the ignition process. The magnitude of the combustion chambers can be adapted to the desired degree of compression. In the case of diesel engines, more than two combustion chambers, four combustion chambers for example, may be formed and a step-down ratio of 4:1 be used so that there will be more time available for the evaporation process.
The injection nozzle and possibly also an ignition device may be arranged around the periphery of the combustion shaft in such a manner that the combustion chambers of the combustion shaft are exposed via an opening to the injection nozzle or the ignition device at a desired time point. In the case of a cylindrical combustion shaft, the injection process is advantageously effected, directly in the radial direction or mainly in the radial direction of the combustion shaft so that an efficient distribution of the fuel in the combustion chamber, which extends in the axial direction of the combustion shaft, can be achieved.
The combustion shaft may, in particular, be in the form of a combustion rotary valve, which advances the compressed fresh gas from the first cylinder volume to the second cylinder volume by virtue of its transporting effect.
For the purposes of supplying fresh gas to the first cylinder volume and/or, if necessary, for discharging the exhaust gas from the second cylinder volume, a suction rotary valve may be provided which is arranged, advantageously, in parallel with the combustion shaft. For example, it may likewise have a portion e.g. a 90xc2x0 segment of its circular cross-section, projecting into the two cylinders, thereby ensuring an efficient supply of fresh gas and possibly a discharge of the exhaust gas over the large connecting surface to the cylinder volumes.
Hereby however, the exhaust gas channel may also be formed in the combustion shaft, advantageously, in the radial center thereof. It is advantageous if only a suction channel and an exhaust gas channel are formed so that the cross sections of these channels need not be made too small thereby maintaining a very low flow resistance. In this case, the suction rotary valve rotates, advantageously, without any step-down ratio relative to the crank shaft so as to enable the fresh gas supply opening therein and possibly also the exhaust gas reception opening therein to be opened relative to the cylinder volume at precisely defined times.
In dependence on the shape of the combustion shaft and possibly that of the suction rotary valve, these may be driven in the same sense or in the opposite sense relative to the crank shaft. In dependence on the angular displacement between the fresh gas supply opening and the expansion opening for expelling the ignited, compressed fresh gas from the combustion shaft, the pistons in the two cylinders may be rotated relative to one another with or without an arbitrary displacement of the tappets or an angular difference of the crank shaft e.g., 90xc2x0, 180xc2x0, 270xc2x0 and so forth. Furthermore, combustion moderators may be employed or catalyzers may be used for the combustion process for the purposes of achieving flameless combustion in the combustion chamber, such as, e.g., a nickel insert element for a mixture of naphtha and water or ceramic inserts, without thereby affecting the cylinder volumes. For example, water may be injected into the combustion chamber in order to lower the temperature of the exhaust gases without thereby causing a considerable loss of pressure.
If the combustion shaft is in the form of a rotary valve, the connecting channels to the plurality of combustion chambers may, in particular, be in the form of a screw thread over the periphery of the rotary valve, whence they are also axially adjacent to one another, so as to increase the advancing effect produced thereby.
Advantageously, the rotary valve is surrounded in sealed manner by a stationery rotary valve housing, which comprises connector openings to the two cylinder volumes.
Due to the use of a rotary valve, whose combustion chambers are only connected to the outlet opening of the first cylinder volume and the inlet opening of the second cylinder volume in certain positions, the construction of valves for controlling these inlets and outlets can be dispensed with so that the manufacturing costs can then be reduced. In addition, due to the fact that the supply of fresh air to the first cylinder volume and the process of expelling the exhaust gases is effected by this or a further rotary valve, the use of valves for controlling the inlets and outlets of the two cylinders can be completely dispensed with so that a cam shaft for these valves will not be necessary. Consequently only the rotary valve or the rotary valves need to be driven by the crank shaft, but a cam shaft having corresponding valves projecting into the cylinder volumes does not need to be driven.
These are merely some of the innumerable illustrative aspects of this present invention and should not be deemed an all-inclusive listing.